1. Field of the Invention
This apparatus relates generally to apparatus for at least partially supporting a portion of a wheeled vehicle and more particularly, but not by way of limitation, to apparatus for adjustably supporting a trailer and which may be retracted or disengaged from the ground or other supporting surface when the trailer is put into use.
2. Description of the Prior Art
Supporting apparatus have utility in facilitating engagement and disengagement of a trailer from a ball or other type trailer hitch mounted on the rear of a truck or automobile. In practice, these apparatus typically provide some means to adjust the height of the trailer above the ground, as with a jack, and to thereby effect or close a vertical separation of the trailer and the usual ball-type trailer hitch. Several such apparatus are disclosed in the prior art. For example, U.S. Pat. No. 2,939,679 to Ryan disclosed a jack mechanism, mounted on the tongue of a trailer-type vehicle, which is vertically retractable when not in use. The jack is disclosed as disposed within a housing member and as engaging a telescoping member slidably received within the housing member. A latch dog is pivotally attached to the housing member, and engages elongated slots in the housing member to bear against a nut which is threaded onto the jack and fits closely within the housing member. Extension of the telescoping member, and a tension spring which is attached to the base plate at the lower end of the telescoping member and to an external portion of the housing member, pass the nut downward past the latch dog and force the top of the nut against the latch dog, thus locking the latch dog into place. Further adjustment of the device is accomplished by rotation of the threaded shaft of the jack through the nut and by bearing of the shaft against a thrust bearing welded across the top of the telescoping member.
Patents to Douglass, U.S. Pat. No. 3,595,527 and Osborne, et al., U.S. Pat. No. 4,216,601, disclose similar devices which employ a tubular support member, with openings disposed therein, attached to the frame of the trailer or other wheeled vehicle. Coarse adjustment of these apparatus is accomplished by positioning ears or radial supporting projections from a first tube slidably disposed in the tubular support member within openings in the tubular support member. Finer adjustments of the apparatus are accomplished by the relative rotation of a jack screw with respect to a second tube slidably disposed within the first tube. The patent to Osborne, et al. also discloses the use of a spring loaded locking mechanism, mounted on the tubular support member, for inserting a pin into selectively alignable openings in the first and second tubes, thereby fixing those tubes into place with respect to the tubular support member and to the frame of the trailer to which the support member is affixed. Patents to Richards, U.S. Pat. No. 2,205,436, and Vinther, et al., U.S. Pat. No. 3,281,160, disclose apparatus employing telescoping tubes and pins which are manually inserted into selectively alignable openings in the tubes.
One of the problems associated with these apparatus as previously disclosed is the absence of convenient means for retracting the innermost telescoping tubular member when any locking means provided are disengaged, and which are durable and not jeopardized by the environment in which the apparatus is employed. For instance, the patents to Osborne et al. and Douglass which were previously discussed require that the user crank or twist something to retract this innermost member from an extended position. The patents to Ryan and to Richards appear to disclose spring means for accomplishing an automatic retraction of the apparatus from a supporting surface, but both spring means are exposed and therefore subject to the influences and interference of the environment.
Such interference can be substantial. For example, an apparatus of the type disclosed in the patents to Ryan and to Richards could be used in a farming operation to support hay wagons or other tractor attachments, where dirt could become caked on the spring or otherwise interfere with the operation of the spring. Such apparatus could also be employed to support a boat trailer, where exposure to water, and particularly salt water, could quickly compromise the utility of such spring means as disclosed in the patents to Ryan and to Richards. The biasing means of the present invention, in contrast, is disclosed as protected from the environment within a third tubular support member, which is in turn slidably disposed within two other tubular members.
Another need not met by the prior art is the provision of a locking mechanism which is variably positionable with respect to the frame or other portion of the vehicle to be supported and which further is conveniently actuated, though the patent to Vinther, et al. does disclose the use of a manually inserted pin which is variably positionable with respect to the frame or other portion of the vehicle to be supported.
The present invention overcomes the shortcomings of the prior art by providing a novel and improved spring loaded drop foot trailer jack which permits coarse and fine adjustment for the height above a supporting surface, which may be locked into a desired position, and which provides means for automatically retracting the jacking apparatus from engagement with the supporting surface with minimal exposure to interference from the environment.